Process for purification of crude light oil



Patented Mar. 12, 1940 UNITED STATES PROCESS FOR PURIFICATION OF CRUDELIGHT OIL Irvin H. Jones, Pittsburgh, Pa., assignor, by mesneassignments, to Koppers Company, a corporation of Delaware No Drawing.Application March 14, 1931,

Serial No. 522,780

'21 Claims. (01. 196-40) This invention relates to the refining orpurification of crude light oil. More particularly, this inventionrelates to the treatment of crude light oil to remove gum forming andcorrosive constituents thereof, and to leave in the refined oil thoseconstituents which are beneficial or at least not harmful so far as theuse of the light oil as a motor fuel is concerned.

One object of my invention is to provide an improved process forremoving from crude light oil substantially all gum forming andcorrosive constituents Without greatly decreasing the yield, and at thesame time obtain a light oil which may beadvantageously used as a motorfuel. A fur- "ther object of my invention is to provide an improvedprocess for refining or purification of crude light oil according towhich substantially all, gum forming and corrosive constituents areremoved while leaving unchanged in the refined oil substantially all ofthose unsaturated compounds whose presence is advantageous in the motorfuel.

In the production of illuminating gas or fuel gas or the like, whetherby a producer or by the distillation of coal to form coke, a number ofcondensib-le hydrocarbon. compounds are givenv oil and carried along bythe gas. It is customary in certain plants to recover from the gascertain of these compounds by washing the gas with a hydrocarbon liquidknown as Wash oil. Various compounds such as benzol are washed out ofthe gas by the wash oil, and may be driven ofi from the wash oil bydistillation. This distillation is carried to a temperature of 180 C. orthe like;

crude-light oil.

Considerable demand has arisen for such lighoil as a fuel for internalcombustion engines. It vaporizes readily, and contains unsaturatedcompounds which have valuable anti-knock properties. The Navy DepartmentSpecifications for motor fuel require that when 100 c. c. are evaporatedto dryness on. an actively boiling steam bath, the gum residue shall notexceed 3 milligrams. To test for corrosiveness, the fuel is evaporated,as above described, in a copper crucible. The copper should not becomediscolored or blackened. An alternative test is to subject a strip ofcopper to boiling light oil to test for dis- 50 coloration or blackeningby the sulphur compounds, which, it is generally considered, constitutethe corrosive agency in the crude light oil.

Heretofore, crude light oil has been refined by 55 ,a process knownas'the silica gel process. Crude 1 and the fraction thus driven ofi isknown as 7 light oil contains a relatively high proportion of variousunsaturated compounds which differ in their physical and chemicalproperties,.as Well I as their stability in storage.

Some are relatively stable compounds, not changing materially on 5 longstanding, while others are so highly reactive and unstable that soonafter production they begin to change from volatile oils to heaviermaterials which are lgummy and resinous in nature. Certain oi the morestab-1e unsaturates couldQwith advantage, be retained in'the refinedproduct, if it is, to be sold as motor fuel, as they have highanti-knock value. On the other hand, no compounds must be left in themotor fuel which will, on long storage, change into gummy 15 in somestep in the process. 25

The special feature of the silica gel process is considered to be thatit removes from the crude light oil all gum forming and corrosiveconstitu ents; and that it leaves unchangedin the refined oil all thoseunsaturated compounds Whose pres- 30 once is advantageous in the motorfuel, since they are considered to have a certain anti-knock value. Itshould moreover be noted that due to the presencein the refined lightoil of these unsaturated compounds the yield is increased by from 10% to15%.

Crude light oil has heretofore been treated with concentrated sulphuricacidto produce refined motor fuel; but it has heretofore been customaryto wash the. crude light oil with sufficient quantities of concentratedacid so that not only were all thegum forming constituents removed fromthe oil but all the unsaturated compounds which produce color withsulphuric acid were removed as Well. This had the disadvantage, 45 thatthe unsaturatedcompounds which have the valuable property of alleviatingknocks in the motor were,to a considerable extent, lost during therefining process.

It has been discovered that the gum forming constituents of the lightoil are particularly sensitive to the presence ofconcentrated sulphuricacid. By conforming my improved process to this attribute or quality ofthe gum forming constituents, I have'made it possible to polymerize allof the gum forming constituents present in the crude light oil withoutusing sufficient acid to attack, to any substantial extent, theunsaturated compounds. Essentially, my improved process relies for thepurification or refining of the crude light oil upon the selectiveseparation of the more unstable unsaturates by washing of the crudelight oil with only small qua titles of concentrated sulphuric acid soas to remove the gum forming and corrosive constituents without removingthe highly desirable unsaturated compounds which have anti-knock valuein the re fined motor fuel.

In order to illustrate my improved process, the following example isgiven: Treat crude light oil for twenty minutes with an acid wash of B.H2804 1% by volume, using sufficient agitation to insure thoroughcontact. After settling, remove this light acid wash. By this treatment,the suspended water and any alkaline bodies, such as ammonia orpyridine, are removed. The crude light oil is then treated with 0.4% byvolume of concentrated H2804 and the mixture agitated for at least anhour, so as to obtain thorough contact of the crude light oil with theacid. The acid sludge is allowed to settle, and is then removed. By thissecond treatment, the more unstable unsaturated compounds arepolymerized and, therefore, are not sufiiciently volatile to pass overwith the refined motor fuel during the subsequent distillation. Thepolymerized unsaturated compounds are left behind in the still residue.In the case of those crude light oils which contain a high percentage ofcoumarone and indene fractions, it is distinctly advantageous to heatthe oil to -70 C. after the treatment with concentrated sulphuric acidand after the separation of the acid sludge. This heat treatment carriesthe polymerization of the unsaturated compounds more nearly tocompletion and, therefore, makes a more stable product. The polymerizedoils are then alkali washed and steam distilled at 98-99 C. Thecondensate is then fractionated, taking the fraction distilled up to andincluding a vapor temperature of 180 C. The proportion of concentratedsulphuric acid to be used in my improved process may vary from as littleas 0.3% to as high as 0.8%. Where the yield is to be as high as possibleand the tolerance for the amount of gum forming and corrosiveconstituents is high, only a small amount of concentrated sulphuric acidis required. With the use of greater quantities of concentratedsulphuric acid, the yield of refined motor fuel is decreased slightlyand the quantity of gum forming and corrosive constituents left in therefined motor fuel is substantially decreased. I prefer to use between0.4% by volume and 0.6% by volume of concentrated sulphuric acid.

Tests show that a crude light oil when treated in accordance with myimproved process will produce a motor fuel which is relatively stable instorage in the dark, whether dehydrated, or in the presence of water, orin the presence of water and iron filings. This motor fuel after fifteenmonths in storage retains its water-white color, and has changed in gumcontent from a maximum of .003 gram to only .008 gram per 100 00., asdetermined by the copper dish test. Moreover, the motor fuel at the endof such storage is practically non-corrosive in response to the coppertest. It is not known whether the sulphur compounds to which corrosionis ordinarily attributed, are still in the light oil; but if so, theyare not in such form as to attack copper.

While I have described one specific manner of performing my improvedprocess, it will be understood that the invention is not restricted tothe particular details of the steps outlined, but may be variouslymodified within the contemplation of the invention and under the scopeof the following claims.

I claim:

1. In the refining of crude light oil comprising essentially a mixtureof motor fuel fractions to make motor fuel therefrom, the process whichcomprises subjecting the crude light oil to treatment to polymerizeunsaturates, said treatment consisting of washing the oil with anamount, between 0.3 and 0.8 per cent by volume of concentrated sulphuricacid sufficient to polymerize the gum forming unsaturates butinsufficient to polymerize the other unsaturates, separating the lightoil from the acid sludge, heating the treated light oil to between 60and C., washing with alkali, and removing volatile constituents of thelight oil by distillation at 98-99 C. while still containing the morestable unsaturates in unpolymerized condition in the oil.

2. In the refining of crude light oil essentially comprising a mixtureof motor fuel fractions to make motor fuel therefrom, the process whichcomprises: subjecting the crude light oil to treatment in the absence ofadsorbent agents to remove unsaturated compounds therefrom, saidtreatment consisting of washing the oil with an amount of mineral acidsufiicient to polymerize all of the gum forming unsaturates present inthe crude light oil but insufficient to attack to any substantial extentthe other unsaturates in the oil then separating acid sludge from therefined oil and washing with alkali prior to distillation to remove theso polymerized gum formers from the refined oil, and completing theseparation of the polymerized gum formers from the oil by distillationwhile still containing the other unsaturated compounds in unpolymerizedcondition in the oil and recovery of the refined distillate as motorfuel oil containing the other unsaturates unpolymerized.

In the refining of crude light oil essentially comprising a mixture ofmotor fuel fractions to make motor fuel therefrom, the process whichcomprises: subjecting the crude light oil to treatment in the absence ofadsorbent agents to remove unsaturated compounds therefrom, saidtreatment consisting of selectively separating the more unstableunsaturates by washing the crude light oil with a small quantity ofconcentrated sulphuric acid sufficient to remove the gum forming andcorrosive constituents but insuificient to remove the highly desirableunsaturated compounds which have anti-knock value in the re fined motoroil, removing the acid sludge, washing with alkali, and then completingthe separation of the refined motor fuel from the polymerized gumformers in the oil by distillation there of while still containing saidhighly desirable unsaturated compounds therein in unpolymerizedcondition.

4. In the process of making motor fuel from crude light oil obtainedfrom coal and comprising essentially a mixture containing motor fuelfractions, which process comprises, treating the crude light oil in theabsence of adsorbents to polymerize unsaturated compounds, saidtreatment comprising washing the oil with between 0.3 and 0.8 per centby volume of concentrated sulphuric acid, removing the acid sludge andthen washing with alkali; and then distilling the oil while still seaves polymerized unsaturated compounds behind in the distillation step.

5. In the process of making motor fuel from crude light oil obtainedfrom coal comprising, treating it in the absence of adsorbents topolymerize unsaturated compounds, said treatment comprising washing theoil with between 0.3 and 0.8 per cent by volume of concentratedsulphuric acid, removing the acid sludge and then washing with alkali,and then distilling the oil While still acontaining the more stableunsaturated compounds in unpolymerized condition in the oil at 98-99 C.leaving the polymerized unsaturated compounds behind in the distillationstep.

6. In the process of making motor fuel from crude light oil obtainedfrom coal comprising, washing it with between 0.3 and 0.8 per cent byvolume of concentrated sulphuric acid, removing the acid sludge, heatingthe oil to 60-7 0 C., after the concentrated acid treatment and afterthe "separation of the acid sludge in the absence of a solid porousadsorbent material, to carry the polymerization of the unsaturatedcompounds more nearly to completion, then washing the oil with alkaliand distilling it while still containing the more stable unsaturatedcompounds in I unpolymerized condition in the oil at 98-99 C.

7. In the process of making motor fuel from crude light oil obtainedfrom coal comprising, washing the'oil with mineral acid in amountsufficient to initiate polymerization of gum forming .,.alkali anddistilling while still containing the more stable unsaturated compoundsin unpolymeriz'ed condition in .the oil to a temperature at which thepolymerized gum formers are not sufiiciently volatile to pass over withthe refined 50 rnotor fuel during the distillation.

8. In the process of making motor fuel from crude light oil obtainedfrom coal comprising, treating the oil in the absence of adsorbents topolymerize the gum forming and corrosive constituents without removingthe highly desirable unsaturated compoundswhich have anti-knock value inthe refined motor fuel, said treatment comprising: washing it withbetween 0.3 and 0.8 per cent by volume of concentrated sulphuric acid,removing the acid sludge, heating the oil to 6040 C., after theconcentrated acid treatment and after the separation of the acid sludgein the absence of a solid porous adsorbent material, to carry thepolymerization of the unsaturated compounds more nearly to completion,then washing the oil with alkali and distilling it while stillcontaining the more stable unsaturated compounds in unpolymerizedcondition in the oil at 9. In the process of making motor fuel fromcrude light oil obtained from coal comprising, treating the oil in theabsence of adsorbents to polymerize the gum forming and corrosiveconstituents without removing the highly desirable unsaturated compoundswhich have anti-knock value in the refined motor fuel, said treatmentcomprising: washing the oil with mineral acid in amount sufficient toinitiate polymerization of gum forming constituents but insuflicient toremove the more stable unsaturated compounds having anti-knock value inmotor fuel, removing the acid sludge, heating the oil to elevated tem-'perature after the acid treatment and after the separation f the acidsludge, to carry the polymerization of the gum forming unsaturatedcompounds more nearly to completion, and thereafter distilling whilestill containing the more stable unsaturated compounds in unpolymerizedcondition in the oil to a temperature at which the polymerized gumformers are not sufiiciently volatile to pass over with the refinedmotor fuel during the distillation.

10. In the process of making motor fuel from crude light oil obtainedfrom coal, the steps comprising: washing the crude light oil withmineral acid in amount suiiicient to initiate polymerization ofgumeforming constituents but insufficient to remove a substantial amountof the more stable unsaturated compounds having high anti-knock value,removing the acid sludge, heating the oil in the absence of a solidporous adsorbent material to a temperature below the decompositiontemperature of gum forming and corrosive constituents in order tocomplete the polymerization said gum forming constituents and raisetheir decomposition points and thereafter continuing the heating todistill while still containing the more stable unsaturated compounds inunpolymerized condition in the oil at higher temperatures but below thedecomposition point of the polymerized constituents, and Washing therefined oil with alkali after the sludge removal step and before thefinal distillation step.

11. In the process of making motor fuel from crude light oil obtainedfrom coal and containing gum forming and corrosive constituents, thesteps comprising: washing the oil with mineral acid in amount sufficientto initiate polymerization of gum forming constituents but insuiiicientto remove a substantial amount of the more stable unsaturated compoundshaving high anti-knock value, removing the sludge, heatingthe oil at arelatively low temperature to polymerize said constituents, andthereafter continuing the distillation while still containing the morestable unsaturated compounds in unpolymerized condition in the oil athigher temperatures but below the decomposition points of thepolymerized constituents, and washing the refined oil with alkali afterthe sludge removal step and before the higher temperature distillationstep.

12. A process as claimed in claim 11 and in which concentrated sulphuricacid is employed as the mineral acid and in amount between 0.3 and 0.8per cent by volume.

13. A process as claimed in claim 11 and in which sulphuric acid isemployed as the mineral acid and in amounts equivalent to 0.4 to 0.6 percent by volume.

14. A process as claimed in claim 11 and in which the low temperature towhich the oil in the absence of a solid porous adsorbent material isheated is between 60-'l0 C. and the higher temperature to which the oilis subsequently heated is equivalent to 98-99 C.

15. A process as claimed in claim ,11 and in which concentratedsulphuric acid is employed as the mineral acid and in amounts between0.3

to 0.8 per cent by volume, and in which the low temperature to which theoil is heated is equivalent to -70 C. and the higher temperature towhich the oil is subsequently heated is equivalent to 98-99 C.

16. In the process of making motor fuel from crude light oil obtainedfrom coal and containing gum forming and corrosive constituents, thesteps comprising, treating the oil with weak sulphuric acid to removesuspended Water and alkaline bodies such as ammonia and pyridine,washing the oil with mineral acid in amount sufficient to initiatepolymerization of gum formconstituents but insuilicient to remove asubstantial amount of the more stable unsaturated compounds having highanti-knock value, removing the sludge, heating the oil in the absence ofa solid porous adsorbent material at a relatively low temperature topolymerize said constituents, and thereafter continuing the distillationwhile still containing the more stable unsaturated compounds inunpolymerized condition in the oil at hi her temperatures but below thedecomposition points of the polymerized consiituents, and washing therefined oil with alkali after the sludge removal step and before thehigher temperature distillation step.

17. The method of refining liquid low boiling hydrocarbon distillatescontaining gum forming constituents consisting in treating thedistillate with an acidic reagent of such concentration and in suchquantity at ordinary temperature and atmospheric pressure as topolymerize only the more easily reactive of the gum forming contituentsand form only a small amount of sludge, separating the sludge from thehydrocarbon, subjecting the treated hydrocarbon while containing thebalance of the acid hydrocarbon reaction products resulting from saidacid treatment in the absence or" a solid porous adsorbent material toan elevated temperature to polymerize the more difficultly reactive ofthe gum forming constituents, and then distilling to separate thetreated hydrocarbon from the polymerized products, thereby obtaining afinal product substantially freed of gum forming constituents.

18 A process of refining crude light oils comprising essentially motorfuel fractions and containing in admixture members of unsaturatedhydrocarbon series belonging to the class distinguished by a relativestableness under normal conditions of storage and members of said seriesthat belong to a class having a tendency to change to substances ofhigher molecular weight under similar conditions of storage, whichcomprises, the steps of subjecting said crude light oils at ordinarytemperature and at atmospheric pressure to reaction with suchconcentration of sulphuric acid in an amount sufficient, not to exceed aquantity about one per cent by volume of the crude oil, to promote theformation of substances of higher molecular weight from the less stableunsaturates but insufiicient to prevent leaving substantially unalteredtherein the unsaturated hydrocarbons possessed of relative stableness instorage, and thereafter separating volatile hydrocarbons from theso-treated light oil in the absence of solid adsorbents for aiding theremoval of the substances of higher molecular weight.

19. In a process of preparing motor fuels from low-boiling oils derivedfrom manufactured fuel gas and the like, said oils comprisingessentially motor fuel fractions and containing in admixture compoundsbelonging to unsaturated series of which some exhibit relative stabilityand of which others tend to change into gummy substances under normalconditions of storage, the method of excluding sensitive gum-formingsubstances from motor fuels volatilized from said oils which comprisesthe step of bringing said low-boiling oils into intimate contact atordinary temperatures and atmospheric pressure with a quantity ofsulphuric acid in aqueous medium sufiicient to alter those members ofthe unsaturated series, that tend to form substantial quantities ofgummy materials under normal conditions of storage, to substances whichexclude them from motor fuels distilled from the acid treated oils, butinsufficient in rsnount to prevent preserving unsaturates that aresubstantially stable in storage in the motor fuel volatilized from saidoils, and thereafter separating by distillation but in the absence ofsolid adsorbents, the altered members from the unaltered members of theunsaturated series.

20. In the method of refining benzol crudes the step which comprisesagitating the crudes with about 0.08 pound of 66 B. sulphuric acid pergallon of the crudes.

21. The method of refining crude benzol which comprises the step ofagitating the crude material for a period of about one hour with about0.08 pound of 66 B. sulphuric acid per gallon of crude benzol.

IRVIN H. JONES.

